Yes, i'd say at least 2. Maybe even consider 3-4. I know they cost, but better to have too much that too little, especially with International requests.

kimmylee I wrote request to Richard Armitage. Hope, his staff will get envelop. So I need SAE. And if photos are 15x20, I have to get (2x) IRCs?

It depends on the celeb or staff dealing with your request.

I'd say you have a good chance if they are willing to use an envelope.

Next time though send the IRC and an envelope with your address on.

I need some advice from expert collectors. I send LOR, 15x20 photos (x3) and IRC (x1) to UK. Without SAE envelope. Have I any chance to get reply? Post administration said that if I get IRC, they can change it to the prepared envelop with stamps. I wrote my address on little piece of paper.